nCov: A Tool for Measuring Length-n Subpath Coverage

Software test adequacy criteria are used to determine whether the test on a software system is sufficient. Code coverage shows how thoroughly a program is tested according to corresponding testing adequacy criteria. There are many coverage criteria used in practice to measure the test adequacy at different granularity of the target program. Length-n subpath criterion is a systematic flexible coverage criterion at a fine granularity. In this paper, we present a prototype test coverage tool named nCov for measuring length-n subpath coverage based on control flow graph. For a C program and corresponding test suite, our tool can measure the length-n subpath coverage for various n, say 1 to 8. It can also be used to select test cases for satisfying length-n subpath coverage with specific n. In addition, to improve the scalability of the tool, we propose a loop compression algorithm to record the program trace. We have conducted a controlled experiment to demonstrate the feasibility and efficiency of our tool.